linux-kernel - Re: [patch 1/3] x86/msi: Make irq_retrigger() functional for posted MSI

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Message-ID: <CAMOZA0LB1UEEib1WWpUW0X-5+LKx28Ko9eGLi5ZSvU8d2yXkBQ@mail.gmail.com>
Date: Tue, 25 Nov 2025 18:54:56 +0100
From: Luigi Rizzo <lrizzo@...gle.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: LKML <linux-kernel@...r.kernel.org>, x86@...nel.org, stable@...r.kernel.org, 
	Lu Baolu <baolu.lu@...ux.intel.com>, Joerg Roedel <joro@...tes.org>
Subject: Re: [patch 1/3] x86/msi: Make irq_retrigger() functional for posted MSI

On Tue, Nov 25, 2025 at 11:20 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> Luigi reported that retriggering a posted MSI interrupt does not work
> correctly.
> [...]
>
> So instead of playing games with the PIR, this can be actually solved
> for both cases by:
>
>  1) Keeping track of the posted interrupt vector handler state

Tangential comment, but I see that this patch uses this_cpu_read()/write()
whereas the rest of the file uses __this_cpu_read()/write()

Given where they are used and the operand size, do we care about
preemption/interrupt protection, or the (possibly marginal) extra cost ?

cheers
luigi